Method for oxidising hydrogen, application of such method, a gas mixture for use therewith and a device for oxidising hydrogen

ABSTRACT

The invention relates to a method for oxidising hydrogen, comprising mixing hydrogen, oxygen and at least one third component, and subsequently reacting hydrogen and oxygen. The invention is characterized in that the at least one third component is carbon dioxide, wherein the method further comprises the step of dividing at least part of said carbon dioxide into CO and 0 radical for controlling the reaction temperature. The invention further relates to a device for oxidising hydrogen gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage of International Patent Application No. PCT/NL2012/050131, filed on Mar. 5, 2012, which claims priority to Netherland Patent Application No. NL 1038653 filed on Mar. 9, 2011, the disclosures of which are hereby incorporated by reference in their entireties.

The present invention relates to a method for oxidising hydrogen according to the preamble of claim 1. The invention further relates to the application of such method according to the invention, to a gas mixture for use therewith and to a device for oxidising hydrogen.

Such a method for oxidising hydrogen is commonly known in the art. This method is used since long on a small scale, but the risk of explosion—uncontrollable and fast oxidation of hydrogen at high temperature—is very large and as a consequence the method has not found industrial application. For example, U.S. Pat. No. 308,276 in the name of Henry M. Paine, describes a method for burning hydrogen gas and oxygen gas, further comprising the addition of a liquid hydrocarbon and subsequently performing the oxidation reaction. Said method is directed to a lighting device. The hydrocarbon provides for a decrease of the combustion rate and yields a colouring of the flame.

Furthermore, U.S. Pat. No. 6,761,558 in the name of Sang-Nam Kim describes a heating device, based on the oxidation of an oxyhydrogen mixture. For preventing a too rapid oxidation of hydrogen, a hydrocarbon (hexane) is metered into the gas mixture.

From US 2010206721 a method is known wherein an oxyhydrogen mixture is produced for metering into the fuel of the gas engine. In this publication, reference is made to the dangerous effects of oxyhydrogen, i.e. that it can lead to backfire. To that end, a safety measure has to be taken. In U.S. Pat. No. 3,982,878 a method is described wherein an inert component is added to the gas mixture so as to lower the reaction temperature obtained in the reaction.

A disadvantage of these known methods is that the hydrocarbons added to the gas mixture provide for additional carbon dioxide emissions. Furthermore, when an incomplete combustion is obtained, soot is formed as well. Since such hydrocarbons are of petrol origin, these methods lead to an increase of the global warming effect.

For obtaining a complete combustion, it is required to use oxygen from the environment, which is a disadvantage. When the combustion is performed in a residential environment, ventilation is of utmost importance.

A further disadvantage of mixing oxyhydrogen with another component according to the state of the art is that the combustion temperature obtained is not constant and is difficult to control.

The invention aims at providing an alternative method of the kind mentioned in the preamble.

The invention especially aims at providing a method as mentioned in the preamble that does not have the disadvantages as mentioned above.

The invention also aims at providing a method wherein the energy contained in the oxyhydrogen mixture can be retrieved completely and in a controlled manner, without producing any additional combustion products (i.e. reaction products).

The invention especially aims at providing a method that allows obtaining a flame with a temperature that can be controlled in the range of from 1100 to 3200 K.

According to a further aspect, the invention aims at providing a method as mentioned in the preamble wherein the combustion rate of the oxyhydrogen mixture can be slowed down without obtaining any additional combustion products (like reaction products).

The invention also aims at providing a method wherein a clean flame is obtained and wherein no soot, nitrogen oxides, of other (optionally detrimental) combustion products.

In the present description, a gas mixture is mentioned that can be used in the method according to the present invention and that can be safely stored, transported and used.

So as to obtain at least one of the goals as mentioned before, according to a first embodiment, the invention provides a method comprising the features according to claim 1. This method has the advantage that water is the only combustion product obtained. The carbon dioxide leaves the reaction in the same state it had entered the reaction. However, the combustion rate of the hydrogen is controllable and manageable, by controlling the concentration of the carbon dioxide at will.

Especially, the advantage is obtained that an, at least to a great extent, closed heating system can be obtained, wherein the water that is yielded from the reaction is divided by means of electrolysis into hydrogen and oxygen which, subsequently, together with the carbon dioxide can be used as combustion mixture. The efficiency of an electrolysis reaction for dividing water into hydrogen and oxygen is very high—as a consequence this method is energetically lucrative.

It has also shown that the invention can be applied in a favourable manner together with carbon dioxide, because carbon dioxide provides a very good controllability of the reaction. It has shown especially that the maximum flame temperature can be decreased by adding carbon dioxide, compared to a gas mixture without carbon dioxide. The amount of energy that is released upon combustion of an oxyhydrogen mixture is equal to the amount of energy released from such oxyhydrogen mixture comprising carbon dioxide. By adding carbon dioxide the reaction rate is slower and the maximum temperature obtained is lower.

The system providing for the decrease of the reaction rate is not completely understood. Without being bound to any theory, it has clearly shown, that the carbon dioxide that has been added to the combustion mixture, is decomposed into CO and O radical. The energy required for this decomposition is retrieved from the reaction of hydrogen with oxygen (obtaining H₂O) from the combustion mixture, as a consequence of which the temperature of the mixture is decreased. The CO₂ as such will take up heat energy from the reaction, so as to be heated. Furthermore, a combination may take place between a hydrogen radical and CO₂, forming an OH and a CO radical. Probably, a decomposition of H₂O may take place combining with an O radical that was obtained from the decomposition of CO₂, so as to obtain two HO radicals. The subsequent recombination of CO and O so as to obtain carbon dioxide (and probably HO radicals as well which also yields water) then yields some further (heat) energy. Due to the delay in the release of energy, the total combustion rate of hydrogen may be lower than the combustion rate of a pure oxyhydrogen mixture. The maximum reaction temperature is decreased as well. This effect according to the present invention is more pronounced than in the case where an inert gas only is added for taking up (thermal) reaction energy. The decomposition into radicals and the subsequent release of the energy (that had been taken up for the decomposition) provides for an improved controllability of the reaction temperature.

It has shown that at a CO₂ concentration of 50% (i.e. a volume ratio of 1 part CO₂ and 1 part other gases) the flame has a maximum temperature of 2110 K. At 63% concentration of CO₂ the temperature is 1676 K, and at 73% concentration of CO₂ the temperature is 1299 K. It is clear that the temperature can be controlled easily by altering the CO₂ concentration in the mixture. The method can be easily made suitable for many applications, from heating purposes to hot air heating and ore melting. Since no oxygen supply from the surroundings is required, the method can even be performed outside the Earth's atmosphere, for example on the moon or on planetoids, and under water.

The method is CO₂ neutral and, as a consequence, is environmentally friendly.

The method according to the invention will be performed in the gaseous state, wherein all components are supplied in the gaseous state. The reaction product will be obtained in the gaseous state as well.

The invention provides the advantage that, at all times, a good reaction is obtained, even when there is no oxygen available from the surrounding area. The method can even be performed at a pressure lower than 1 atmosphere, for example outside the Earth's atmosphere or under water. A further advantage is that no harmful components are produced during the reaction. The method therefore can even be performed in a dwelling area. An additional advantage is that no oxygen from the surroundings is consumed.

Because the amount of CO₂ in the starting mixture is known, it can easily be calculated if, and if so during what time, the amount of CO₂ can be expelled freely into the dwelling area.

According to a preferred embodiment, the ratio of hydrogen:oxygen is in the range of from 200:80 to 200:120, preferably 200:100, measured at normal conditions. In that case, a suitable combustion of hydrogen is obtained. A stoichiometric amount of oxygen or a small excess of oxygen ensures that no carbon is produced from the carbon dioxide as supplied to the reaction.

Furthermore, it is preferred that the ratio of oxygen:carbon dioxide is in the range of from maximally 1000:1 to minimally 1:100, so as to obtain a convenient temperature and delay of the reaction rate, such that the reaction is controllable or even can be inhibited. For example, the ratio can be maximally 500:1, preferably maximally 100:1, or even maximally 50:1. The ratio can be preferably minimally 1:80, more preferably minimally 1:50 or even less. Any ratio of components as mentioned in this description is to be understood as being a volume ratio of such components. Where applicable, any ratio is measured at normal conditions.

According to a further aspect, the invention relates to a gas mixture to be used in a method according to the invention or in an application of the method according to the invention for heating purposes, as mentioned in claim 4, comprising hydrogen, oxygen and carbon dioxide, wherein the ratio of hydrogen:oxygen is in the range of from 200:80 to 200:120 and the ratio of oxygen:carbon dioxide is in the range of 1:<47, that is 1 part oxygen to less than 47 parts carbon dioxide.

A method for producing a gaseous mixture for use in a method according to the invention may comprise the step of subjecting to electrolysis an aqueous solution of carbon dioxide. The carbon dioxide that is dissolved in water, will be released upon electrolysis and provides a gas mixture when combined with said oxygen and hydrogen which may suitably be used in the method according to the invention.

It is especially preferred that the method for producing a gas mixture comprises the step of subjecting to electrolysis an aqueous solution of carbon dioxide.

The method for obtaining a reaction mixture, that is the gas mixture, may comprise an embodiment wherein the solution is a saturated aqueous solution of carbon dioxide. This way, a simple gas mixture is obtained that is not combustible and explosive at the onset of electrolysis, such that the gas mixture can be managed extremely well and easily.

Finally, the invention relates to a device for oxidising hydrogen gas, comprising at least one connection for a source of oxygen, hydrogen and carbon dioxide, preferably separate connections for each of hydrogen, oxygen and carbon dioxide. Such a device can be easily made. The device may be principally identical to known burners for gases that can be oxidised, like acetylene burners or methane burners. When a single connection for a source of a gas is provided, only one control valve is required. When a multitude of connections for several sources is provided, each connection needs its own control valve so as to be able to control the ratio of said gases as required.

Such a device may advantageously be provided with a single connection for a source of hydrogen, oxygen and carbon dioxide, wherein said connection may be connected to an electrolysis device for subjecting an aqueous solution of carbon dioxide. When the solution comprises carbon dioxide in a concentration that enables the gas mixture obtained for use in the oxidation reaction of hydrogen and oxygen, the gas obtained may be used instantaneously; in that case a further control of the amounts of gas components is not required.

An alternative embodiment is provided by such a device comprising a connection for a source of hydrogen and oxygen and a connection for a source of carbon dioxide. This provides the advantage that the ratio of carbon dioxide to the oxyhydrogen gas may be controlled, so as to alter the flame characteristics as required.

A ratio of oxyhydrogen:carbon dioxide of about 1:1 unexpectedly seems to provide a mixture that has burning characteristics that resemble that of natural gas. However, the caloric value of hydrogen is clearly different from that of natural gas, to wit 11.5 MJ/m³ in the case of hydrogen and 31.65 MJ/m³ in the case of natural gas. As a consequence, it was expected that a larger amount of hydrogen would be required to provide a gas mixture with corresponding burning characteristics.

Hereafter, the invention will be elucidated by means of a few examples.

EXAMPLE I

Purified water was subjected to electrolysis at room temperature. The hydrogen gas and oxygen gas obtained were collected together in a container.

The gas mixture was subsequently ignited by means of a lighter's flame. The ignition took place instantaneously with a colourless to light blue flame.

EXAMPLE II

An aqueous solution of carbon dioxide (about 8 g CO₂ per litre of water) was subjected to electrolysis at room temperature. The gas mixture obtained, comprising oxygen, hydrogen and carbon dioxide, was collected in a container. The carbon dioxide is released preferentially during electrolysis, such that the concentration of carbon dioxide in the gas mixture collected in the container during the first phase (until about 10% of the solution had been subjected to electrolysis) was higher than in subsequent phases.

A gas mixture with a ratio of hydrogen:oxygen:carbon dioxide of 4:2:94 or a smaller amount of hydrogen (the ratio of hydrogen:oxygen remains mainly constant) yields no hydrogen oxidation. A smaller amount of carbon dioxide does provide a combustible mixture.

The combustion rate is noticeably slower at a highest concentration carbon dioxide at which combustion still takes place, compared to a lower concentration of carbon dioxide. As a consequence, the combustion of an equal amount of carbon dioxide will take longer than of a gas mixture comprising a lower concentration of carbon dioxide. Furthermore, the maximum reaction temperature is lower at a higher concentration carbon dioxide than at a lower concentration carbon dioxide.

Performing the reaction when using a gradually smaller concentration of carbon dioxide provides a colour of the flame that shifts from blue, via purple to bright orange, which is an indication of an increasing reaction temperature and a decreasing proportion of carbon monoxide oxidation (to carbon dioxide).

The invention can be applied in industry and in domestic appliances. In particular in cases of surplus of electricity, the method according to the invention can be applied to perform electrolysis of water using said surplus so as to decompose the water into hydrogen and oxygen (both in a gaseous state). Carbon dioxide can be added to the gas mixture when pure water is used, but an aqueous solution of water may be used as well. The method may be used in heating apparatuses, kilns, heating burners, welding apparatuses, cutting torches and the like. Using carbon dioxide in an amount to be determined by a person skilled in the art, the oxyhydrogen mixture can be added to natural gas and be combusted in burners that are commonly used for natural gas combustion.

The gas mixture according to the invention can be stored, transported and used more safely than pure oxyhydrogen gas (a stoichiometric mixture of hydrogen and oxygen). For example, hydrogen and oxygen can be stored and transported separately from each other, wherein to one, or both, of them carbon dioxide is added. This provides for the possibility that the gas mixture is produced at a central site and transported to individual users.

A gas mixture according to the invention can be suitably produced at an energy surplus, for example by means of electricity that is produced by wind energy or solar energy. The mixture can be stored as required or be used in natural gas-fired power plants or be combusted in a dwelling place as direct heating means. The combustion does not derive any oxygen from the environment, whereas the precautionary measures can be taken as mentioned hereinabove.

The invention is not restricted to the embodiments as mentioned above. The invention is restricted to the appended claims only.

The phrase “natural gas” as mentioned here relates to a gas mixture that is distributed in the Netherlands as natural gas during the priority date of the present patent application.

The invention provides a method for reacting hydrogen and oxygen safely and in a controllable manner. The well-known oxyhydrogen explosion is inhibited effectively and simply. The hydrogen combustion energy can be effectively used for heating purposes and further applications where reaction heat is required. The effect of the addition of carbon dioxide on the reaction rate probably is due to the reaction equilibrium of CO₂ into CO radicals and the interaction of CO with other radicals present in the reaction.

The method according to the present invention provides the opportunity to control the reaction temperature continuously by controlling the carbon dioxide concentration. This is a great advantage with respect to the combustion of natural gas, in which case both the caloric value and the air composition have a large influence on the reaction temperature.

The invention extends to every combination of separate combination of features and measures mentioned independently from each other in this description. It is explicitly mentioned that where reference is given to hydrogen and oxygen, both components are used in the gaseous state for oxidising said hydrogen with oxygen, according to common practice and as known in the art. 

1. A method for oxidising hydrogen, comprising mixing hydrogen, oxygen and at least one third component, and subsequently reacting hydrogen and oxygen, wherein the at least one third component is carbon dioxide; wherein the method further comprises a first step of dividing at least part of said carbon dioxide into CO and O radical and a second step of combining said CO and O radical into carbon dioxide for controlling the reaction temperature.
 2. A method according to claim 1, wherein the volume ratio of hydrogen:oxygen is in the range of from 200:80 to 200:120, preferably 200:100.
 3. A method according to claim 1, wherein the volume ratio of oxygen:carbon dioxide is in the range of from 100:1 to 1:100, preferably in the range of from 100:1 to 1:<47.
 4. Application of a method according to claim 1 for heating by means of a gas mixture comprising hydrogen and oxygen in a volume ratio in the range of from 200:80 to 200:120, wherein the mixture furthermore comprises carbon dioxide, and wherein the volume ratio of oxygen:carbon dioxide is in the range of from 100:1 to 1:<47.
 5. A gas mixture to be used in a method according to claim 1, comprising hydrogen, oxygen and carbon dioxide, wherein the volume ratio of hydrogen:oxygen is in the range of from 200:80 to 200:120 and the ratio of oxygen:carbon dioxide is in the range of 1:<47.
 6. A device for oxidising hydrogen gas, comprising at least one connection for a source of oxygen, hydrogen and carbon dioxide, preferably separate connections for each of hydrogen, oxygen and carbon dioxide.
 7. A device according to claim 6, wherein a single source of hydrogen, oxygen and carbon dioxide has been provided and comprises an electrolysis device for electrolysis of an aqueous solution of carbon dioxide.
 8. A device according to claim 6, wherein a connection for a source of hydrogen and oxygen and a connection for a source of carbon dioxide have been provided.
 9. A device according to claim 6, wherein a first connection for a source of hydrogen and a second connection for a source of oxygen and carbon dioxide have been provided.
 10. A device according to claim 6, wherein a first connection for a source of oxygen and a second connection for a source of hydrogen and carbon dioxide have been provided.
 11. A device according to claim 6, wherein a first connection for a source of hydrogen and carbon dioxide and a second connection for a source of oxygen and carbon dioxide have been provided.
 12. Use of a device according to claim 6 by performing a method for heating purposes, said method comprising: mixing hydrogen, oxygen and at least one third component, and subsequently reacting hydrogen and oxygen, wherein the at least one third component is carbon dioxide, wherein the method further comprises a first step of dividing at least part of said carbon dioxide into CO and O radical and a second step of combining said CO and O radical into carbon dioxide for controlling the reaction temperature.
 13. Use according to claim 12, comprising the step of controlling the volume ratio of carbon dioxide to oxygen, such that combustion provides a flame temperature in the range of from 1100 to 3200 K preferably a temperature of from 1299 to 3200 K.
 15. A method according to claim 1, wherein oxygen and hydrogen are obtained from separate sources, and wherein at least one source comprises a mixture with carbon dioxide.
 16. A gas mixture to be used in an application as mentioned in claim 4, comprising hydrogen, oxygen and carbon dioxide, wherein the volume ratio of hydrogen:oxygen is in the range of from 200:80 to 200:120 and the volume ratio of oxygen:carbon dioxide is in the range of 1:<47. 